Seal for x-ray tubes



Dec 20, 1927.

C. T. ULREY SEAL FOR X-RAY TUBES Filed Jan. 1926 R ARE 7 INVE (IL/9770A T/P/DL ATTORNEY FIGZ FIGJ

Patented Dec. 20, 1927.

UNITED STATES PATENT OFFICE.

CLAYTON TRIDLE ULREY. OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTING- HOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

SEAL FOR X-RAY TUBES.

Application filed January 13, 1926. Serial No. 80,932.

This invention relates to gastight seals between glass and metal and more particularly to forming such a seal between a hollow body of metal and a hollow body of glass.

In the manufacture of such devices as X-ray tubes and other discharge devices, it is desirable to seal a hollow metallic body to the glass walls of the envelope or to a flare tube. In making the seal between the glass and the metal, it has been the practice to merely insert one end of a hollow glass body within a hollow body of metal, the walls of the two bodies being disposed in parallelism. The seal is then produced by heating the metal body to a red heat and then blowing air into the hollow glass body to force the glass, which has become plastic through contact with the heated metal, against the inner walls of the hollow metallic body. thus fusing the two bodies together. Although good seals can at times be made in this manner, it not infrequently happens that the seals are imperfect due to air bubbles being entrapped betweenthe glass and the metal, such bubbles not being afl orded an opportunity of escaping prior to the, fusing of the glass to the metal adjacent the upper edge of the metal body. It has been found that by flaring the metal body adjacent the edge which is sealed to the glass body, that this difficulty is avoided, thus providing seals free from entrapped air bubbles.

Therefore it is an object of the present invention to provide a simple method whereby it is possible to form seals between glass and metal without the danger of air bubbles being entrapped therebetween.

A further object to the invention is to provide a seal for X-ray tubes and the like which may be expeditiously manufactured and in which the seal is gas-tight and free from entrapped bubbles.

Other objects of the invention will become apparent as the following description is read.

Referring to the drawings for a better understanding of the invention,

Fig. 1 is a vertical sectional view of a seal as previously constructed and prior to the fusion of the glass to the metal.

Fig. 2 is a view, similarto Fig. 1, after the fusion of the glass to the metal and showing entrapped air bubbles between the glass and metal.

Fig. 3 is a vertical sectional view of the present invention showing the position of the hollow glass body within the hollow metal body prior to producing the seal, and

Fig. 4 is a vertical sectional view of a seal manufactured in accordance with the present invention.

The present invention as described hereinafter, relates particularly to the manufacture of seals for X-ray tubes and the like and in this connection, there is illustrated in Figs. 1 and 2 of the drawings a hollow cylindrical body 5 having a solid shank 6, into which is secured by a threaded connection 7, a stem 8 to which a radiator, not shown, may be attached. The cylindrical body 5 has projecting outwardly therefrom an annular flange 9 having a reduced end 11 of such thickness. preferably about .008. that it will stretch with the glass when the latter expands and contracts. This reduced portion 11 is sealed to a glass tube 12. An annular inwardly projecting shoulder 13 is provided to serve as a stop; so as to limit the distance the glass tube 12 is inserted within the annular flange 9.

The flange 11 is principally made of copper although other metals, such as chromium, a chromium alloy, or a nickel-iron core coated with copper or chromium, may be employed.

In making the seal, the glass tube 12 is inserted within the annular flange 9 until the lower edge 14 rests against the stop 13, there after the two bodies are rotated in a flange 15 which is directed against the lower edge of the reduced section 11 of the annular flange of copper. The copper becomes heated to a red heat which results in the glass becoming plastic. Air is then admitted within the glass tube 12 to bring the plastic glass into firm contact with the reduced section 12, thus forming the seal.

It is obvious that in making a seal in this manner wherein the walls of glass and metal are in parallelism, as illustrated in Figs. 1. and 2, there is a certain amount of air disposed between thcse walls. Owing to the fact that the glass may be of the same plasticity throughout the entire mass disposed within the reduced section 11, the sealing between the glass and metal may take place at a point above the stop 13, prior to sealing adjacent the stop 13, thus preventing the air disposed between the glass and the metal from moving outwardly at the upper edge 16, with the result that the. seal is rendered imperfect by the presence of air bubbles 11', as illustrated in 2.

According to the present invention good seals may be produced Without danger oi: entrapping the air bubbles this being accomplished by outwardly flaring the reduced portion 11 so that the glass Walls and the annular wall of metal 12 are not in pa allelism and furthern'iore so that there is a slight space 18' between the glass 12 and the upper edge 15 of the outwardly timed metal wall 11.

With this construction, it Will be obvious that when the Home 15 is applied adjacent to the annular stop 13 end the metal wall 11 heated to rel heat thst the glass at the lower end 1;1 oi the glass tube 12 will have a liigher degree 0t plasticity than the glass adjacent the upper edge is of the annular Ila e 11 so that V*ll8l1"tll6 air is admitted Witlnn the tubular glass body 12 the glass Will be pressed Ergo-inst the motel body 11 gradually from the portion thereof Where it contacts with the stop 13 to th upper edge 16 of the annular flange 12 thus forcing the air between the glass and the metal outweirdly through the space 18 between the gloss and the metal. in this manner a ready exit is always provided for any oi? the air between the glass and the metal.

It is possible by reason 01: the present invention to manufacture the seals in'e more expeditious manner and furthermore to always secure seals free from entrapped air bubbles.

Although the invention'hss been described with particular reference to aseal for an X-ray tube it is obvious that the some is applicable to the production of seals for any hollow body which is desired to be sealed to FL hollow body metal.

lilodificetions of the present invention may occur to those skilled in the art, however, such inoc'lificutions are contemplated as coming' Within the invention as defined by the claims appended hereto.

What is claimed is:

1. The method 01 settling e hollow body of glass to metal which comprises 3' Xteposing the gloss and metoh heating the metal and rendering the gloss plastic and thcree' ter forcing the glass against the metal by b ing the edge of the gloss against the metnl and then gmduolly bringing the reu'iziinder of the glass thereogsinst.

2. The method of sealing a tubular body of glass to a tubular body of metal which comprises i nserting the tubular body of glass within the tubular body of metal so that the edge of the tubular body only contacts with the tubular body of metal. he "1g; said in'etslto oihiggh teniperuture by directing thune against the meted ut the place Where k cont: itherervith nd tl'iereu'tter forcing the glass by sir pr urc into con tact with the metal;

The method of forming aseal between tubular tss body and a tubular metal. body free from entruppednir bubbles Which coinp 7 temperature endsimultaneously heating the body to plasticity, and fusing the metal body to the ss body by bringing; thetivo into rontect b air pressure, soidycontsc, being e1 cted by gradually, laying the g body against the injetelbody end permit the some time the air disposed between the two bodies to exude therefrom udjoccnt the edge of the metal body,

4-. The method of uniting it glass tube and :1; metulutubewhich consistsiin outwardly llziringthe' netsl tube and Welding the glass tube to said: outwardly flared portioniby first 'oin'in the end of theolziss tube to the 1132."

row portion otthe flared port of the metal tube and then gradually laying the gloss of the glass tube against the flared portion. outwardly toward the edge of the flared part of the metal tube A seal for tubular gloss and metal bodies comprising {L body of metal such copper having an annular flange reduced in thickness, an annular stop adjacent the lower edge of said annular flange and a tubular gloss body sealed to said annuler flange.

In testimony whereof, l: have hereunto subscribed iny name this 12th of January, 19%.

Comm return mm:

esheuting the met-qt body to a high til) 

